Spark plug



Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to improvements in spark plugs, and has particular reference to a spark plug wherein the heat incident to sparking will be conductedaway from the porcelain or other insulators and will therefore prevent expansion and breakage of the porcelain.

The principal object of this invention is to produce a spark plug which will have a relatively long life without renewal'or adjustment, in comparison with the standard form of spark plug.

A further object is to produce a spark plug which may be used in a manner similar to standard spark plugs.

A further object of the invention is to produce a spark plug that is provided with a large sparking surface and a plurality of arcing points.

An additional object of the invention is to produce a unique spark plug construction wherein both arcing points being outside the plug and in the sweep of explosive gases, will be kept cool and free of carbon, and will not short circuit.

Other objects and advantages will be apparent during the course of the following description.

In the accompanying drawing forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Figure l is a side elevation of my improved spark plug having a portion thereof broken away,

Figure 2 is a bottom plan view of Fig. 1,

Figure 3 is a fragmentary perspective view of one of the electrodes,

Figure 4 is a modified form of my device,

Figure 5 is a bottom plan view of Fig. 4,

Figure 6 is a fragmentary view of the electrodes used in the modified form of my device, and

Figure '7 is an enlarged fragmentary detail view showing the serrated surface of the electrode.

The ordinary spark plug consists of an electrode centrally positioned in a porcelain insulator and an electrode extending from the shell of the plug into a position adjacent the other electrode, so that a spark may jump across the gap between the two electrodes. The result of this construction is that the heat incident to the spark causes the first mentioned electrode to become exceedingly hot and to therefore expand to a much greater degree than the expansion of the porcelain insulator, and as a result, this expansion causes the porcelain surrounding the electrode to crack and to often short circuit the plug. I have therefore carried the electrode beyond the same so that the sparking occurs at a point between the electrode and the shell, so remote that there is practically no heat derived from sparking conducted thru the electrode, the only heat present being that of combustion which is substantially a thousand degrees less than the heat caused by sparking, and not injurious to the plug.

In the accompanying drawing wherein for the purpose of illustration is shown a preferred embodiment of my invention, the numeral 5 designates a portion of the engine in which is secured a shell 6 of the plug, while centrally positioned within this shell is a porcelain or other insulator '7. A conductor 3 extends thru the porcelain or 2 other insulator 7 and is sealed therein. This conductor is secured to a terminal 9 and carries at its lower end an electrode 11, which electrode is provided with arms 12 and 13, which arms are bent so as to form semi-circular portions 14 and 16 respectively and have serrations 15 which lie parallel to the edge of the shell 6 which is also serrated as best illustrated in Fig. 2, as at 20. In the modified form shown in Fig. 4, the electrode 17 is bent upon itself so as to provide a portion 18 parallel to the edge of the shell 6. Due to this construction, when a spark occurs, the same will take place between the serrated surfaces 15 and 20 of the electrode and the edge of the shell of the spark plug at a point so far from the porcelain or other type of insulators, that the heat caused by the spark will not be conducted back thru the arms 12 and 13 of the electrode 11 to the conductor 8, and therefore, the conductor 8 will not expand sufficiently to cause breakage of the porcelain insulator.

The operation of both forms is identical and consists essentially of removing the spark from the porcelain or other type of insulators so that the heat thereof cannot be conducted back thru the electrode.

It will be observed from this construction that as either electrode is wasted away, the other points will readily come into play, and that by virtue of having the arms lie substantially parbeen cracked, nor has there been any indication or tendency along these lines.

Experience has shown that the life and 6111- ciency of spark plugs, such as used on internal combustion engines, is in almost every instance limited to the life of the porcelain or other insulators, which insulates and supports the central terminal, that is, it has generally been taught that the continued exposure of the porcelain to the internal heat of the engine, sooner or later causes cracking or breaking of the same, hence short circuiting the sparking terminals, etc.

General experience and observation on my part show that the cracking of the procelain in nine cases out of ten invariably takes place near the lower end of the porcelain and that this cracking is not altogether due to the internal heat or temperature of the engine, but is more frequently caused by the added heat conducted from the spark gap. I have found that the central terminal in most spark plugs extends a comparatively short distance beyond the end of the porcelain and that due to this fact overheating and excessive expansion takes place, thus cracking the lower end of the porcelain. It should further be understood that the heat produced in the spark gap has a temperature of several thousand degrees greater than the temperature produced during the explosion of the fuel charge, and that this heat is readily conducted by the central terminal and that excess expansion and cracking of the porcelain or other insulator, will naturally take place. Accordingly, by providing the central terminal of such length and shape as described, the conducted heat of the spark gap may be entirely dissipated by radiation and conduction to the surrounding atmosphere or fuel charge.

It is to be understood that the forms of my invention herewith shown and described are to be taken as a preferred example of the same and that various changes relative to the material, size, shape and arrangement of parts may be resorted to without departing from the spirit 0! the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In a device of the character described, a spark plug having an insulating member and a shell surrounding said insulating member, of a conductor extending thru said insulating member and having an electrode formed integral therewith and extending away from said insulator, and an arm formed on said electrode, a portion of said arm lying parallel with the shell of said plug, and spaced therefrom, the portion of said arm lying parallel with the shell of said plug being of a curved formation and being limited to the arc of a circle andlying in a plane below said shell,

2. In combination with a sprak plug having an insulated member positioned within the metallic shell thereof, said shell having a serrated lower edge, of a conductor extending through said insulator and projecting considerably beyond said shell, upwardly and angularly extending arms integrally formed with said conductor and terminating in an electrode, said electrode consisting of integrally formed semi-circular members disposed in opposite directions in a horizontal plane immediately below the shell, and said electrode members having serrated sections facing the serrated section of the shell of the plug.

3. In a device of the character described, a spark plug having an insulating member, a conductor extending through said insulating member and having an electrode formed integral therewith and extending away from said insulating member, an arm formed on said electrode, a portion of said arm lying parallel with the shell of said plug and in a plane below and in opposed relation with the lowermost outer edge of said shell, and the portion of said arm lying parallel to the shell being of curved formation and limited to an arc of a circle.

JAMES EDWARD HEALEY. 

